Halogenation of mineral carbides, hereinafter carbides, has been used to produce microporous carbon materials with remarkably narrow pore size distribution as described in US20020097549. According to the international standards (IUPAC) the micropores are with the size of less than 20 Å (1 Å=0.1 nm). Pore size maximum of these materials may be as low as 6-7 Å. The carbide-derived microporous carbons are very attractive materials in several important application fields like gas and liquid purification from contaminating impurities, specially those having small-size atoms or molecules; storage of small-size molecules such as hydrogen and methane; desalination of drinking water such as method applying flow-throw capacitors; electric energy storing devices such as batteries and capacitors, etc.
The important issue within most of porous carbon applications is the quantity of pores with desired pore size in bulk volume of carbon. In fact the microporous carbide-derived carbon, usually made at temperature below 800-900° C., contains considerable amount of too small pores below 6-7 Å as shown in FIG. 1, which normally are not accessible in practical adsorption processes. The peak pore size is suggested to be adjusted within few angstroms by changing the carbide chlorination temperature [Gogotsi et al. Nature Mat., Vol. 2, p. 591 (2003)]. However, in practice the increased chlorination temperature reflects not only in the shift of the peak pore size but also in widening of the pore size distribution. The latter fact is usually undesired, while resulting in the lost molecular sieve behaviour of the carbide-derived carbon. Furthermore, the temperature initiated pore size shift not necessarily avoids formation of the inaccessible very small micropores. One can achieve substantial shift in the average pore size at reaction temperatures above 900-950° C., however, the high temperature values support the rearrangement of the carbon atoms into higher ordered nanostructures, thereby noticeably decreasing the quantity of micropores and the active surface in total volume of the carbon.
Prior art in PCT/EP03/04202 teaches how to enlarge the small micropores in highly microporous carbide-derived carbon by subsequently performed specific oxidation in very small micropores. However, when the carbon to be treated is too nanoporous and therefore difficult to saturate with the oxidising agent, the method is not effective enough or needs to be repeated several times. This results in the undesired resources consumption and increased cost of the final carbon material.
It is thus an object of this invention to provide a cheaper and more productive method for making the microporous carbon-derived carbon with improved access in micropores.
It is a further object of this invention to provide an improved carbon with a narrow pore size distribution.